The present invention generally relates to cylinder and/or valve deactivation and two-step variable valve lift systems in internal combustion engines. More particularly, the present invention relates to a roller finger follower rocker arm device that accomplishes valve deactivation and/or cam profile mode switching in internal combustion engines.
Deactivation roller finger followers (RFFs) typically include a body and a roller carried by a shaft. The roller is engaged by a cam of an engine camshaft that causes the RFF body to pivot, thereby actuating an associated engine valve. The deactivation RFF is selectively switched between a coupled and a decoupled state. In the coupled state the shaft is coupled to the body, and rotation of the output cam is transferred from the roller through the shaft to pivotal movement of the RFF body, which, in turn, reciprocates the associated valve. In the decoupled state, the shaft is decoupled from the body. Thus, the shaft does not transfer rotation of the output cam to pivotal movement of the RFF body, and the associated valve is not reciprocated. Rather, the shaft is reciprocated within grooves formed in the RFF body. The grooves retain and guide the reciprocation of the shaft.
A two-step RFF operates in a manner similar to a deactivation RFF, as described above. However, one particular difference between the operation of a deactivation RFF and a two-step RFF occurs in the decoupled mode of operation. The body of a deactivation RFF is typically engaged by zero-lift cam lobes. In the decoupled mode, the zero-lift cam lobes simply maintain the deactivation RFF body in a static position. Thus, the associated engine valve is not reciprocated. The body of a two-step RFF is engaged by associated low-lift cam lobes. In the decoupled mode, the body of the two-step RFF is pivoted by the low-lift cam lobes. The pivoting of the body of the two-step RFF in the decoupled mode, in turn, reciprocates the associated engine valve according to the lift profile of the low-lift cam lobe.
Lost motion springs maintain contact between the roller and the output cam when either type (i.e., deactivation or two-step) of RFF is in the decoupled mode. The lost motion springs engage the shaft and the body of the RFF. The springs bias the shaft and roller against the output cam, and absorb the reciprocal motion of the shaft and roller. However, lost motion springs add undesirable width to conventional RFF""s. Furthermore, movement of the lost motion springs causes wear and friction where the springs contact the body of the roller finger follower. Even further, the side load capacity of conventional RFF""s may not be suitable for some applications. Moreover, as the shaft reciprocates within the grooves, movement, or play, of the shaft within the grooves in a direction generally transverse to the body may result in binding of the shaft and/or misalignment of the locking pin assembly, thereby making it difficult to re-couple the shaft to the body.
Therefore, what is needed in the art is an RFF having a reduced width for use in applications with limited space.
Furthermore, what is needed in the art is an RFF that reduces friction and wear through sliding contact between the lost motion springs and the body.
Even further, what is needed in the art is an RFF having increased side load capacity.
Even further, what is needed in the art is an RFF that reduces play of the shaft in a direction transverse to the grooves and/or body.
Still further, what is needed in the art is an RFF that reduces the potential for locking pin assembly misalignment, thereby improving the reliability of mode switching in the RFF.
Moreover, what is needed in the art is an RFF that reduces the likelihood of the shaft binding within the grooves, thereby improving the reliability of mode switching in the RFF.
The present invention provides a deactivation and/or two-step roller finger follower for use with an internal combustion engine.
The invention comprises, in one form thereof, an elongate body having a first side member and a second side member. A bracket having first and second sides is associated with the body. The first side of the bracket is disposed adjacent an inside surface of the first side member of the body. The second side of the bracket is disposed adjacent an inside surface of the second side member of the body. A roller is disposed between the first and second sides of the bracket. The roller defines a shaft orifice therethrough. An elongate hollow shaft extends through the shaft orifice and couples the roller to the bracket. A locking pin assembly is disposed at least partially within the hollow shaft. The locking pin assembly has a first position wherein the shaft is decoupled from the body and a second position wherein the shaft is coupled to the body. The locking pin assembly is switchable between the first and second positions.
An advantage of the present invention is that the RFF has a reduced width for use in applications with limited space.
Another advantage of the present invention is that the RFF eliminates the need for washers to retain the needle bearing needles.
Still another advantage of the present invention is that RFF reduces friction and wear through sliding contact between the lost motion springs and the RFF body.
Yet another advantage of the present invention is that the RFF has increased side load capacity.
A further advantage of the present invention is a reduction of play of the shaft in a direction transverse to the grooves/body of the RFF, and thus increased reliability in mode switching of the RFF.
An even further advantage of the present invention is a roller finger follower with a reduced likelihood of locking pin misalignment, and thus increased reliability in mode switching of the RFF.